Exeter Chiefs playmaker Henry Slade has suffered a suspected broken leg after being carried off 15 minutes into their match against Wasps.
The Chiefs ran out 41-27 winners to move top of the Aviva Premiership, but the injury to one of the brightest young talents in England has marred the victory.
"He is in a cast and the initial prognosis is that it looks likely to be a broken leg," Chiefs coach Rob Baxter told reporters.
"Obviously until we get him back to Exeter and get the X-rays done, we won't know for sure what the damage is, but we're pretty confident there is something nasty there.
A broken leg would rule Slade out of the Six Nations and is a major blow to new coach Eddie Jones' plans.